Problem 2
What do the following indicators tell you about whether a reaction can proceed as written? (a) The standard free-energy change is positive. (b) The free-energy change is positive. (c) The reaction is exergonic.
Problem 4
What conditions are necessary for the free-energy change to be used to predict the spontaneity of a reaction?
Problem 6
Why is it necessary to define a modified standard state for biochemical applications of thermodynamics?
Problem 11
For the hydrolysis of ATP at \(25^{\circ} \mathrm{C}(298 \mathrm{K})\) and \(\mathrm{pH} 7, \mathrm{ATP}+\mathrm{H}_{2} \mathrm{O} \rightarrow \mathrm{ADP}+\mathrm{P}_{1}+\mathrm{H}^{+},\) the standard free energy of hydrolysis \(\left(\Delta G^{\circ}\right)\) is \(-30.5 \mathrm{kJ} \mathrm{mol}^{-1}\left(-7.3 \mathrm{kcal} \mathrm{mol}^{-1}\right),\) and the standard enthalpy change \(\left(\Delta H^{\circ \prime}\right)\) is \(-20.1 \mathrm{kJ} \mathrm{mol}^{-1}\left(-4.8 \mathrm{kcal} \mathrm{mol}^{-1}\right)\) Calculate the standard entropy change \(\left(\Delta S^{\circ}\right)\) for the reaction, in both joules and calories. Why is the positive sign of the answer to be expected in view of the nature of the reaction? Hint: You may want to review some material from Chapter 1.
Problem 14
The \(\Delta G^{\circ}\) for the reaction Citrate \(\rightarrow\) Isocitrate is \(+6.64 \mathrm{kJ} \mathrm{mol}^{-1}=+1.59 \mathrm{kcal} \mathrm{mol}^{-1} .\) The \(\Delta G^{\mathrm{o}}\) for the reaction Isoci- trate \(\rightarrow \alpha\) -Ketoglutarate is \(-267 \mathrm{kJ} \mathrm{mol}^{-1}=-63.9 \mathrm{kcal} \mathrm{mol}^{-1} .\) What is the \(\Delta G^{\text {or }}\) for the conversion of citrate to \(\alpha\) -ketoglutarate? Is that reaction exergonic or endergonic, and why?
Problem 19
Organize the following words into two related groups: catabolism, energy- requiring, reductive, anabolism, oxidative, energyyielding.
Problem 21
Would you expect the production of sugars by plants in photosynthesis to be an exergonic or endergonic process? Give the reason for your answer.
Problem 22
Would you expect the biosynthesis of a protein from the constituent amino acids in an organism to be an exergonic or endergonic process? Give the reason for your answer.
Problem 23
Adult humans synthesize large amounts of ATP in the course of a day, but their body weights do not change significantly. In the same time period, the structures and compositions of their bodies also do not change appreciably. Explain this apparent contradiction.
Problem 24
Identify the molecules oxidized and reduced in the following reactions and write the half reactions. (a) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CHO}+\mathrm{NADH} \rightarrow \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{OH}+\mathrm{NAD}^{+}\) (b) \(\mathrm{Cu}^{2+}(\mathrm{aq})+\mathrm{Fe}^{2+}(\mathrm{aq}) \rightarrow \mathrm{Cu}^{+}(\mathrm{aq})+\mathrm{Fe}^{3+}(\mathrm{aq})\)
